Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$203.51	4.844%	$213.368	$213.37	$213.35	$213.40
Purchase #2	$117.55	9.598%	$128.8324	$128.83	$128.85	$128.80
Purchase #3	$156.75	4.813%	$164.2944	$164.29	$164.30	$164.30
Purchase #4	$26.40	10.360%	$29.135	$29.14	$29.15	$29.10
Purchase #5	$76.94	7.369%	$82.6097	$82.61	$82.60	$82.60
Purchase #6	$19.69	3.477%	$20.3746	$20.37	$20.35	$20.40
Purchase #7	$73.65	13.238%	$83.3998	$83.40	$83.40	$83.40
7 purchase totals =	$674.49		$722.0139	$722.01	$722.00	$722.00